A large number of mutations have been isolated which affect the phototransduction process in D. melanogaster. Such mutants are of importance in understanding certain clinical conditions. Many disorders of the human eye are genetic in orgin, and animal models are extremely valuable to inquire into the genetic bases of these disorders. Drosophila mutants exists which exhibit phenotypes analogous to those observed in human retinal degenerative diseases, such as retinitis pigmentosa. Conditions found in certain forms of color blindness (protanopia and deuteropia) are also observed in several types of Drosophila photoreceptor mutants. The initial objective of the proposed study is to isolate cloned segments of Drosophila DNA from two gene loci known to be involved in photoreceptor function (the norp A and nina E loci). The molecular organization of these genes will be examined in wild type genomic DNA, in addition to DNAs isolated from a large number of different nina E and norp A mutants. In this way it should be possible to determine how changes in the organization and structure of these genes is correlated with photoreceptor potential defects, altered behavioral response, and blindness. The complex complementation pattern observed for nina E mutations will be examined at the molecular level to ascertain whether or not the nina E region contains several distinct but related genes involved in phototransduction. The long term experimental plan also includes the subsequent isolation and characterization of nina E and norp A RNA transcripts and protein products. D. melanogaster DNA sequences exist which appear to be homologous to several cDNA clones prepared from bovine retina mRNA. These bovine homologous regions of the Drosophila genome will be isolated to study their possible genetic role in retina structure and/or function.